linux-kernel - Re: [PATCH] perf_events: fix errors path in perf_output

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <AANLkTinvvU2G-KxSK6cAU-fYQyCF1m_5i282oq8rbJ8-@mail.gmail.com>
Date:	Mon, 17 May 2010 13:57:25 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	John Kacur <jkacur@...hat.com>
Cc:	linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu,
	paulus@...ba.org, davem@...emloft.net, fweisbec@...il.com,
	acme@...radead.org, perfmon2-devel@...ts.sf.net, eranian@...il.com
Subject: Re: [PATCH] perf_events: fix errors path in perf_output_begin()

On Mon, May 17, 2010 at 1:04 PM, John Kacur <jkacur@...hat.com> wrote:
>
>
> On Mon, 17 May 2010, Stephane Eranian wrote:
>
>>   In case the sampling buffer has no "payload" pages, nr_pages is 0.
>>   The problem is that the error path in perf_output_begin() skips to
>>   a label which assumes perf_output_lock() has been issued which is
>>   not the case. That triggers a WARN_ON() is perf_output_unlock().
>>
>>   This patch fixes the problem by adding a new label and skipping
>>   perf_task_unlock() in case data->nr_pages is 0.
>
> It does? Your code looks good to me, but the description above is
> a little flawed, since no new label is added.
>
Sorry about that. I had written the text before the final version of the patch!
I will resubmit.

>> --
>> diff --git a/kernel/perf_event.c b/kernel/perf_event.c
>> index a4fa381..95137b6 100644
>> --- a/kernel/perf_event.c
>> +++ b/kernel/perf_event.c
>> @@ -3035,8 +3035,10 @@ int perf_output_begin(struct perf_output_handle *handle,
>>       handle->nmi     = nmi;
>>       handle->sample  = sample;
>>
>> -     if (!data->nr_pages)
>> -             goto fail;
>> +     if (!data->nr_pages) {
>> +             atomic_inc(&data->lost);
>> +             goto out;
>> +     }
>>
>>       have_lost = atomic_read(&data->lost);
>>       if (have_lost)
>> --
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/